Condenser



Jan. 18, 1949. w. E. McCOWN 2,459,332

' connnusmz Filed April 5, 1946 3 Sheets-Sheet l ATTORNEY W. E. M COWN CONDENSER Jan. 18, 1949.

Filed April 5 1946 3 Sheets-Sheet 2 iNvENToR f. M (Em w,

ATTORNEY Jan. 18, 1949. w. E. MCCQWN 2,459,332

CONDENSER Filed April 5, 1946 3 Sheets-Sheet 3 Ex 1m;

REID I l i T a a a 3 I INVENTOR /t. MZ'an M BY .hezm

ATTORNEY Patented Jan. 18, 1949 CONDENSER William E. McCown,

Haddonfleld, N. J., assignor to Radio Corporation oi America, a corporation of Delaware Application April 5, 1946, Serial No. 659,707

9 Claims.

This invention concerns a slidable condenser construction especially designed for use between the conductors of a concentric transmission line. The condenser construction provides a path of very low impedance for high frequency energy; in effect, a short circuit. In order to enable the variation of the effective length of the concentric transmission line the construction is made slidable.

Briefly stated, the condenser of the invention comprises a plurality of spaced annular discs connected together electrically in parallel relation and secured together mechanically to form an integral unit adapted to be positioned between and slidable over the lengths of the conductors of the concentric line. Each disc of the .condenser is made of suitable high dielectric material, such as Mycalex, and both sides of each disc are coated by metal deposits (preferably silver) with a circular marginal area free of the metal coating. Themarginal area on one side of the annulus disc is adjacent the central aperthe disc is adjacent the outer periphery. Thus, the creepage distance or path between the metallic coats, on opposite sides of the disc is increased by the width of the marginal area. The difl'erent discs which compose the condenser are similarly arranged in parallel planes with insulating cups separating adjacent discs. Direct rod-like connections are provided between metallic coatings which face the same direction.

An annular brush comprising a plurality of resilient-contact springs forms one terminal of the condenser for engaging the inner conductor of the concentric line, while a larger annular brush of somewhat similar construction forms the other terminal of the condenser for engaging the outer conductor of the concentric line. These inner and outer conductors of a concentric transmission line.

Fig. 2 is a side elevation view of the condenser construction of Fig. 1 with the outer conductor ture, while the marginal area on the other side of of the concentric line broken away to illustrate the details of the condenser.

Fig. 3 shows one side of one annulus disc of the condenser.

Fig. 4 shows the opposite side of the annulus disc of Fig. 3.

Fig. 5 is a section of Fig. 1 along the line AA.

Fig. 6 is a section of Fig. 1 along the line 18-13.

Fig. '7 is a diagrammatic and simplified showing of the electrical circuit equivalent of the condenser construction of the invention, and shows its use between the inner and outer conductors of a concentric transmission line for varying the efl'ective length thereof.

Throughout the figures of the drawing the same parts are represented by the same reference numerals.

The invention may be better understood by first referring to the equivalent electrical diagram of the condenser shown in Fig. 7. The condenser construction comprises a plurality of equally spaced annular discs I, 2 and 3. These discs are of identical constr ction, each comprising a suitable high dielectric material (such as Mycalex), one side of which iscoated with a metallic deposit 4 (such as silver), while the other side is coated with a metallic deposit 5 of the same electrically conducting material. The silver coating 4 on each disc is deposited uniformly and electrically continuously over the dielectric material, except for a marginal area 1 adjacent the outer periphery of the disc. The silver coating 5 is deposited uniformly and electrically continuously over the opposite side of the disc except for a marginal area 8 adjacent the aperture of the annulus. The metallic coatings I of the discs I, 2 and 3 face in the same direction and are electrically connected together by direct connections -9. The metallic coatings 5 on the opposite sides of the disc also face in the same direction but opposite with regard to the directions faced by the coatings 4. These coatings 5 are connected together electrically by direct connections I0. It will thus be seen that the condenser unit is composed of three discs which are connected electrically in parallel relation in order to triple the capacity of one disc alone.

The disc I at one end of the condenser con- 0 struction has securely fastened thereto an annular brush ll composed of a plurality of resilient contact springs which engage the inner conductor ii of a concentric'transmission line. At

the other end of the condenser construction,

. accassa nular brush I2 which is securely fastened to the metallic coating I and which is also composed of a plurality of resilient contact springs engaging the inner surface of the outer conductor I8 of the 'high frequency current carrying line, or, if desired, a concentric line resonator of suitable dimensions usually having an efiective electrical length of one-quarter of a wavelength at the operating frequency.

Fig. 3 shows in detail the construction of one side of each of the discs I, 2 and 3 of the condenser. It should be noted that the silver coatin 4 is adjacent the central aperture of the annulus and that there is a marginal area 1 free of the metallic coating adjacent the outer periphery.

Fig. 4 shows the opposite side of the disc of Fig. 3 with the silver coating 6 adjacent the outer periphery of the disc and an uncoated marginal area 8 free of the metallic'coatin'g. Each disc is provided with eight holes 20, passing through the entire thickness of the disc for enabling metallic bolts to pass therethrough. The semicircular portions 2i on the sides of the disc, it should be noted, are free of metallic coating. In these semi-circular portions are positioned insulating cups 22 which serve as spacers between the discs I, 2 and 3, as shown in more detail in Figs. 1, 2, 5 and 6.

Referring to Fig. 5, which shows a section along the line A-A of Fig. 1, it will be seen that the silver coatings 4 which face the same direction are directly connected together by means of a metallic bolt 9' which passes through all three discs. This bolt is directly connected to each coating 4 through a metallic threaded nut 23 and a metallic washer 24. The insulating cup-like spacers 22 in Fig. 5 are so positioned that their wide portions rest on the semi-circular portions 2| of the marginal areas 8 adjacent the central apertures of the disc.

Referring to Fig. 6, which shows a section along the line B-B of Fig. 1, it will be noted that the silver coatings 5 of the three discs I, 2 and I are.

directly connected together by means of a metallic bolt III which passes through all three discs. This bolt I is directly connected to the silver coating of each disc through a metallic, threaded nut 23 and a metallic washer 24. The insulating cups 22 in Fig. 8 have their wide portions resting upon the semi-circular portions ii of the marginal areas 1' adjacent the peripheries of the discs.

It will thus be seen there are eight symmetrically positioned insulating cups 22 between each pair of adjacent discs; four symmetrically positioned insulating cups being positioned on the upper side of the disc I, and four symmetrically positioned insulating cups on the lower side of the disc 3.

An inspection of Figs. 1 and 2 will show that the annular brush II has its resilient contact 4 springs extending all the way around the inner conductor I! of the concentric transmission line, while the annular brush I2 has several of the resilient contact springs omitted on opposite sides i of this annular brush at the locations at which the racks I! are fastened. The omission of certain ones of these resilient contact springs in annular brush I2 does not interfere with the operation of the short-circuiting slider construction of the invention. There are a sufllcient number of contact springs in the annular brush l2 to make good electrical contact between the inner surface of the outer conductor I8 of the concentric transmission line and the condenser unit.

In one embodiment of the invention successfully tried out in practice, the condenser unit of the invention was used in a concentric line resonator in a frequency modulation broadcast transmitter producing a power output in the neighborhood of one to three kilowatts. This frequency modulation broadcast transmitter was used to transmit electromagnetic waves having frequencies of the order of 88 to 109 megacycles.

What is claimed is:

l. A condenser comprising an annulus of di electric material, coatings of highly electrically conducting metallic material deposited on opposite sides of said annulus. one of said coatings extending from the outer edge of said annulus to a circular marginal area free of said coating and located adjacent the central aperture of the annulus, the other coating extending from the central aperture of the annulus to a circular marginal area free of said coating and located adjacent the outer edge of the annulus, said annulus having its inner and outer edges free of metallic material, an annular brush mechanically linked and electrically connected to one coating, and another annular brush mechanically linked and electrically connected to the other coating, said annular brushes having different diameters.

2. A condenser comprising an annulus of dielectric material, coatings of highly electrically conducting metallic material deposited on opposite sides of said annulus, one of said coatings extending from the outer edge of said annulus to a circular marginal area free of said coating and located adjacent the central aperture of the annulus. the other coating extending from the central aperture of the annulus to a circular marginal area free of said coating and located adjacent the outer edge of the annulus, said annulus having its inner and outer edges free of metallic material, an annular brush mechanically linked and electrically connected to one coating, and another annular brush mechanically linked and electrically connected to the other coating, said annular brushes having diilerent diameters and each comprising a plurality of resilient contact springs.

3. A condenser comprising an annulus of dielectric material, coatings of highly electrically conducting metallic material deposited on opposite sides of said annulus, one of said coatings extending from the outer edge of said annulus to a circular marginal area free of said coatings and located adjacent the central aperture of the annulus, the other coating extending from the central aperture of the annulus to a circular marginal area free of said coating and located adjacent the outer edge or the annulus, a terminal for said condenser comprising a slidable contact element mechanically linked in rigid manner and electrically connected to one coating, another ter- 2,4sass2 minal; for said condenser comprising another slidable contact element mechanically linked in rigid manner and electrically connected to the other coating, said contact elements being located on opposite sides of said annulus.

4. A condenser comprising an annulus of dielectric material, coatings of highly electrically conducting metallic material deposited on opposite sides of said annulus, one of said coatings extending from the outer edge of said annulus to a circular marginal areairee of said coating and located adjacent the central aperture of the annulus, the other coating extending from the central aperture 0! the annulus to a circular marginal area tree of said coating and located adja cent the outer edge of the annulus, said annulus having its inner and outer edges free of metallic material, an annular brush mechanically linked and electrically connected to one coating, and

another annular brush mechanically linked and electrically connected to the other coating, said annular brushes having different diameters and each comprising a plurality oi resilient contact springs, the contact springs of one annular brush facing in a direction opposite to that faced by the contact springs of the other annular brush.

5. A condenser comprising an annulus of dielectric material, coatings oi highly electrically conducting metallic material deposited on opposite sides of said annulus, one of said coatings extending from the outer edge oi said annulus to a circular marginal area tree of said coating and located adjacent the central aperture of the annulus, the other coating extending from the central aperture of the annulus to a circular. marginal area tree of said coating and located adjacent the outeredge of the annulus, another similarly constructed annulus of dielectric material spaced from said first annulus and similarly arranged in a parallel plane, a plurality of insulating spacers between said two annulus members, threaded bolts passing through said insulating spacers and interconnecting similarly arranged coatings of metallic material, nuts threadedly engaging said bolts and rigidly linking said annuli, a terminal for said condenser comprising a slidable contact element mechanically linked in rigid manner and electrically. connected to one coating of one annulus, another terminal for said s condenser comprising another slidable contact element mechanically linked in rigid manner and electrically connected to a non-corresponding coating of the other annulus, said contact elements being located on opposite sides of said condenser.

6. A condenser comprising a plurality of simi--- lar annuli of dielectric material similarly arranged coextensively in spaced parallel planes, a plurality oi dielectric spacers between adjacent annuli, each" annulus having coatings 0! highly electrically conducting metallic material deposited on opposite sides oi said annulus, one coating of an annulus extending from the outer edge of said annulus to a circular marginal area tree oi said coating and located adjacent the central aperture oi the annulus, the other coating of the annulus extending from the central aperture of the annulus to a circular marginal area free of said coating and located adjacent the outer edge of the annulus, each annulus having its inner and outer edges free 01 metallic material, bolts passing through said spacers and interconnecting similarly arranged coatings oi! metallic material on the diiierent annuli, means secured to said bolts and rigidly linking said annuli together, an annular contact membermechanically linked and electrically connected to the outer coating on one end annulus, and an annular contact member mechanically linked and electrically connected to the outer coating on the other end annulus, one annular contact member having fingers arranged in a circle whose diameter is larger than the diameter of said annuli, while the other annular contact member has contact fingers arranged in a circle whose diameter is smaller than the central apertures 01 said annuli.

7. A condenser comprising an annulus of dielectric material, coatings of highly electrically conducting metallic material deposited on opposite sides of said annulus, one of said coatings extending from the outer edge of said annulus to a circular marginal area free of said coating and located adjacent the central aperture of the annulus, the other coating extending from the central aperture of the annulus to a circular marginal area free of said coating and located adjacent the outer edge of the annulus, said annulus having its inner and outer edges free of metallic material, an annular brush mechanically linked and electrically connectedto one coating, and another annular brush mechanically linked and electrically connected to the other coating, said annular brushes having contact fingers arranged in circles, the circle formed by the fingers of one brush having a diameter larger than the, diameter of said annulus, while the circle formed by the fingers oi the other brush has a diameter smaller than the diameter oi the central aperture of the annulus.

8. A' condenser comprising an annulus 0! dielectric material, continuous coatings of highly electrically conducting metallic material deposited on opposite sides of said annulus, one of said coati'ngsextending .i'rom the outer edge of said annulus to a circular marginal area free of said a coating and located adjacent the central aperture marginal area free of said coating and located adjacent the outer edge oi the annulus, each side of said annulus having a plurality of spaced substantially semi-circular areas therein which are free of said coating and which extend into the continuous coating on that side, another similarly constructed annulus of dielectric material spaced from said first annulus and similarly arranged in a parallel plane, a plurality of insulating spacers between said two annulus members and resting on said semi-circular areas, threaded bolts passing through said insulating spacers and interconnecting similarly arranged coatings oi metallic mate- -rial, nuts threadedly engaging said bolts and rigidly linking said annuli, a terminal for said condenser comprising a slidable'contact element mechanically linked in rigid manner and electrically connected to one coating of one annulus, another terminal for said condenser comprising another slidable contact element mechanically linked in rigid manner and electrically connected to a non-corresponding coating of the other annulus, said contact elements being located on opposite sides of said condenser.

9. A. condenser comprising a flat plate of dielectric material having a central aperture, coatings of highly electrically conducting metallic material deposited on opposite sides of said fiat plate, one of said coatings extending from the outer edge or said plate to a circular marginal area free of said coating and located adjacent the central aperture oi the plate, the other coating extending from the central aperture of the plate to a marginal area free of said coating and located adjacent the outer edge oi the plate, said plate having its inner and outer edges tree of metallic material, a hollow brush mechanically linked and electrically connected to one coating and another hollow brush mechanically linked and electrically connected to the other coating, said hollow brushes having diflerent cross-sectional dimensions across the hollow areas thereof.

WILLIAM E. McCOWN.

8 amaaucas man The following reiierences are of record in the file of this patent:

UNITED STATES PA'IENTS Number Name Date 2,331,193 Hutcheson Oct. 5, 1943 2,348,693 Minnium May 9, 1944 2,407,147 F'edotofi Sept. 3, 1946 2,415,850 Samuel Feb. 18, 1%?

mama: PATENTS Number Country Date 518,127 Great Britain Feb. 19, 1940 

